/*
 * Copyright 2001-2005 (C) MetaStuff, Ltd. All Rights Reserved.
 *
 * This software is open source.
 * See the bottom of this file for the licence.
 */

package com.googlecode.bluetools.dom4j.io;

import com.googlecode.bluetools.dom4j.Element;
import com.googlecode.bluetools.dom4j.ElementHandler;

/**
 * <p>
 * <code>PruningElementStack</code> is a stack of {@link Element}instances which will prune the tree when a path
 * expression is reached. This is useful for parsing very large documents where children of the root element can be
 * processed individually rather than keeping them all in memory at the same time.
 * </p>
 * 
 * @author <a href="mailto:james.strachan@metastuff.com">James Strachan </a>
 * @version $Revision: 1.1 $
 */
class PruningElementStack extends ElementStack {
	/** ElementHandler to call when pruning occurs */
	private ElementHandler elementHandler;

	/**
	 * the element name path which denotes the node to remove from its parent when it is complete (i.e. when it is
	 * popped from the stack). The first entry in the path will be a child of the root node
	 */
	private String[] path;

	/**
	 * The level at which a path match can occur. We match when we have popped the selected node so the and the
	 * lastElementIndex points to its parent so this value should be path.length - 2
	 */
	private int matchingElementIndex;

	public PruningElementStack(String[] path, ElementHandler elementHandler) {
		this.path = path;
		this.elementHandler = elementHandler;
		checkPath();
	}

	public PruningElementStack(String[] path, ElementHandler elementHandler, int defaultCapacity) {
		super(defaultCapacity);
		this.path = path;
		this.elementHandler = elementHandler;
		checkPath();
	}

	public Element popElement() {
		Element answer = super.popElement();

		if ((lastElementIndex == matchingElementIndex) && (lastElementIndex >= 0)) {
			// we are popping the correct level in the tree
			// lets check if the path fits
			//
			// NOTE: this is an inefficient way of doing it - we could
			// maintain a history of which parts matched?
			if (validElement(answer, lastElementIndex + 1)) {
				Element parent = null;

				for (int i = 0; i <= lastElementIndex; i++) {
					parent = stack[i];

					if (!validElement(parent, i)) {
						parent = null;

						break;
					}
				}

				if (parent != null) {
					pathMatches(parent, answer);
				}
			}
		}

		return answer;
	}

	protected void pathMatches(Element parent, Element selectedNode) {
		elementHandler.onEnd(this);
		parent.remove(selectedNode);
	}

	protected boolean validElement(Element element, int index) {
		String requiredName = path[index];
		String name = element.getName();

		if (requiredName == name) {
			return true;
		}

		if ((requiredName != null) && (name != null)) {
			return requiredName.equals(name);
		}

		return false;
	}

	private void checkPath() {
		if (path.length < 2) {
			throw new RuntimeException("Invalid path of length: " + path.length + " it must be greater than 2");
		}

		matchingElementIndex = path.length - 2;
	}
}

/*
 * Redistribution and use of this software and associated documentation ("Software"), with or without modification, are
 * permitted provided that the following conditions are met:
 * 
 * 1. Redistributions of source code must retain copyright statements and notices. Redistributions must also contain a
 * copy of this document.
 * 
 * 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the
 * following disclaimer in the documentation and/or other materials provided with the distribution.
 * 
 * 3. The name "DOM4J" must not be used to endorse or promote products derived from this Software without prior written
 * permission of MetaStuff, Ltd. For written permission, please contact dom4j-info@metastuff.com.
 * 
 * 4. Products derived from this Software may not be called "DOM4J" nor may "DOM4J" appear in their names without prior
 * written permission of MetaStuff, Ltd. DOM4J is a registered trademark of MetaStuff, Ltd.
 * 
 * 5. Due credit should be given to the DOM4J Project - http://www.dom4j.org
 * 
 * THIS SOFTWARE IS PROVIDED BY METASTUFF, LTD. AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL METASTUFF, LTD. OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * 
 * Copyright 2001-2005 (C) MetaStuff, Ltd. All Rights Reserved.
 */
